1. Field of The Invention
The present invention relates to an oil passage structure in the transmission casing of an automotive automatic transmission in which oil passages intercommunicating the oil pump, provided for supplying operating oil, a valve assembly having a control valve for controlling flow paths of the operating oil from the oil pump and an oil pressure regulator valve for regulating the oil pressure from the oil pump are integrally formed.
2. Description of The Prior Art
As is generally known, the conventional automotive automatic transmission includes an oil pump assembly which is traditionally disposed in the vicinity of the abutting portion between the transmission casing accommodating the gear train and the torque converter housing containing the torque converter assembly therein.
FIG. 1 is a partial sectional view illustrating a conventional automatic transmission having an oil pump assembly including an oil pump housing 20, an oil pump cover 21, an inner gear (drive gear) 17, an outer gear (driven gear) 18, and a stationary crescent 19 integrally formed with the oil pump housing 20. Also referring to FIG. 1, reference numeral 1 designates a torque converter assembly which includes a converter cover 2, a pump impeller 3, a turbine runner 4, and a stator 5. The pump impeller 3 is fixed to the outer periphery of the converter cover 2 by welding. The turbine runner 4 is secured to a turbine hub 6 at a flange portion thereof by riveting. The turbine hub 6 is splined to the end of the transmission input shaft 11. The stator 5 is provided between the pump impeller 3 and the turbine runner 4 to form a torque converter. The stator 5 is mounted in a hollow stationary sleeve 8 via a one way clutch 7. The stationary sleeve 8 permits the transmission input shaft 11 to extend therethrough while maintaining an annular space therearound.
The torque converter assembly 1 is accommodated in a torque converter housing 14 which is firmly secured to the transmission casing 15 by means of bolts 25. The oil pump cover 21 extends radially from the stationary sleeve 8. Within the pump housing 20, oil pump elements including an inner gear 17 and an outer gear 18 are operatively disposed. The oil pump cover 21 is secured to the pump housing 20 by means of bolts 23 in such a manner as to accommodate the oil pump body 16 in conjunction with the pump housing 20. A pump driving sleeve 9 extends into the pump housing 20 and is journalled through a bushing 10 fixed on the inner peripheral surface of the pump housing 20. The pump driving sleeve 9 permits the stationary sleeve 8 to extend therethrough. The pump driving sleeve 9 includes one axial end drivingly connected to the pump impeller 3 and the opposing end splined to the inner gear 17. Since the pump driving sleeve 9 is spaced from the stationary sleeve 8, an annular oil passage 12 is defined between the two sleeves 8 and 9. This passage 12 at its one end communicates with the inside of the pump impeller 3 and at its opposite end communicates with the outlet port of the oil pump body 16 through a pressure regulator valve (not shown) via an oil passage structure including a plurality of oil passages formed in the pump cover 21. Oil in the inside of the pump impeller 3 flows out of the turbine runner 4. The oil discharged from the turbine runner 4 flows to an annular oil passage 13 and thereafter the oil is fed from the passage 13 to the pressure maintaining valve (not shown) for maintaining the oil pressure within the torque converter assembly 1 at a certain determined level. Although not shown in FIG. 1, after flowing through the oil maintaining valve, the oil will flow to the oil cooler mounted within the radiator of the vehicle. After being cooled by the oil cooler, the oil will be distributed in the transmission to the various portions to be lubricated and thereafter flow back to the oil reservoir (not shown). In this manner, the torque converter performs its torque multiplying function because oil maintained at a certain pressure will transmit the required torque through the action of the stator 5 from the pump impeller 3 to the turbine runner 4.
The rotation of the crankshaft (not shown) of the internal combustion engine is always delivered to the pump impeller 3 through the converter cover 2. The rotation of the pump impeller 3 is delivered through the pump driving sleeve 9 to the inner gear 17 engaging with the outer gear 18. In this manner, the oil pump operates as long as the engine operates.
As clearly seen in FIG. 1, the pump cover 21 mates the transmission casing 15 at the outer perimeter thereof, in such a manner that the pump cover 21 is firmly secured to the transmission casing 15 at the mating surface 22 between the casing 15 and the cover 21 by means of bolts 24. As previously described, the operating oil is supplied from the outlet port of the oil pump body 16 to the valve assembly including an oil pressure regulator and a control valve through the oil passage structure formed in the pump cover 21. There have been proposed and developed various oil passage structures for communicating the oil pump with the valve assembly.
One such oil passage structure is shown in FIG. 2. Referring to FIG. 2, reference numeral 26 designates an opening formed on the mating surface 22 of the transmission casing 15. The opening 26 is connected through the oil passage defined in the oil pump cover 21 to the outlet port of the oil pump body 16. The opening 26 is communicated with the inlet port of the valve body 27 through a substantially T shaped communication passage which includes a horizontal channel 28 and a vertical channel 29. The horizontal channel 28 at one end communicates with the opening 26 and at an opposite end is closed by a plug (not shown) in an air tight fashion.
Another oil passage structure has been disclosed in Japanese Utility Model (Jikkai) Showa No. 60-7360. This oil passage structure includes a plurality of oil passages formed in a torque converter housing at the outer peripheral section of the converter housing which is sandwiched between the outer perimeter of the oil pump housing and the outer periphery of the transmission casing.
In these conventional oil passage structures, complicated machining of high accuracy is required and in addition auxiliary parts, such as plugs are required. Furthermore, due to the placement of the oil pump and valve assembly, the positioning options for the opening 26 and the two channels 28 and 29 are severely limited, resulting in a low degree of freedom of design with regard to the oil passages of the transmission casing 15.